1. Field of the Invention
This invention relates to materials for removing suspended impurities. More particularly, this invention relates to an organic polymeric adsorbent of an ion exchange resin or an adsorbing material having a unique surface and surface layer structure and morphology and by which suspended impurities chiefly comprised of metallic oxides present in trace amounts in water which, for example, is to be treated to make ultrapure water can be removed with a remarkably increased efficiency. Generally speaking, the metallic oxides in condensate water are mainly composed by iron oxides which are called as "crud" or "crud iron". This invention also relates to a use of that polymeric adsorbent or adsorbing material, and to a method of removing suspended impurities employing that polymeric adsorbent or adsorbing material.
2. Description of the Prior Art
In order to enable the interior of boilers used in steam power generating facilities to be always kept clean, the condensate water returning from the condensing turbine to the boiler is highly purified with a condensate demineralizer before it is supplied as cooling water into the boiler.
The condensate demineralizer is of a "mixed bed" type in which a cation exchange resin and an anion exchange resin are packed in admixture. Impurities in condensate water, i.e., ionic components and suspended solid components (chiefly comprised of fine particulate metal oxides), are separated by ion exchange and by adsorption and filtration so as to purify the condensate water. In this regard, ion exchange resins may be classified as organic polymeric adsorbents. Mixed beds of cation and anion exchange resins have conventionally been formed by using resins in gel form and/or porous and/or macroreticular resins.
In the conventional method of using particulate ion exchange resins, impurities such as ionic components and metal oxides that are adsorbed or trapped by ion exchange resins are removed by periodical regenerations with chemicals or through mechanical back washing so as to maintain in a clean condition the condensate demineralizer.
While the efficiency of removing impurities from condensate water is important as regards both ionic components and metal oxides, enhanced separation of metal oxides such as crud iron has recently become particularly important for the operation of boiling water nuclear power generating facilities in steam power generating facilities. Separation is carried out for the purpose of reducing the dose of radioactivity to which operators are exposed during periodical inspections of the plant at the outage by reducing the amount of metal oxides carried over from the cooling water into the nuclear reactor. It has, however, been found that this need cannot be met by the prior art method of using conventional particulate ion exchange resins since it is not highly effective for removing metal oxides.